A Hall device usually has the form of a plate, but not necessarily. This plate consists of conducting material provided with at least four electrical contacts at its periphery. A bias current I is supplied to the device via two opposite contacts, called the current contacts. The two other contacts are placed at two equipotential points at the plate boundary. These contacts are called the voltage contacts or the sense contacts. If a magnetic field perpendicular to the surface is applied to the device, a voltage appears between the sense contacts due to the Hall effect. This voltage is called the Hall voltage. An example of a Hall device is shown in FIG. 1, where for the basic function only the contact pairs AC and BD are used.
A major problem of Hall devices is their offset voltage. The offset voltage is a static or a very low frequency output voltage at the sense contacts of the Hall device in the absence of a magnetic field. The causes of offset voltages in integrated Hall devices are imperfections of the fabrication process and nonuniformity of materials. An offset reduction method according to the state of the art is the switched spinning current method. This method uses a Hall plate with eight or more contacts which are symmetrical with respect to rotation by e.g. 45.degree.. The direction of the current is made to spin discretely by contact commutation. Averaging the consecutive Hall voltages reduces the offset.